. Congenital and acquired lesions of the retinalpigment epithelium

摘要

The retinal pigment epithelium (RPE) is derived from neuroepithelium. At approximately the fifth week of gestation the primary optic vesicle invaginates to form the optic cup. The inner layer gives rise to the retina, non-pigmented ciliary epithelium, and iris pigment epithelium. The retinal pigment epithelium, the pigmented ciliary epithelium and iris muscles, are derived from the outer layer. The retinal pigment epithelium is the first tissue of the body to become pigmented, at about the fourth week of gestation1.The retinal pigment epithelium is a monolayer of hexagonal-shaped, low-cuboidal cells whose basement membrane forms the inner layer of Bruch's membrane. The apical villous processes of the epithelium closely appose the outer segments of the photoreceptors. The retinal pigment epithelium has many functions including absorption of light, metabolism of vitamin A, phagocytosis of rod and cone outer segments, formation of an acid-mucopolysaccha-ride complex that surrounds the outer segments of the rods and cones and metabolite transport, and it is the site of the blood ocular barrier of the outer circulation.